The invention relates to a device and process for producing a soldered joint between two joining partners which can be joined via a common contact surface, using a solder material which can be introduced between the two joining partners.
For permanent, strong joining of two joining partners consisting of metal or metal-like materials, it is customary to employ a known soldering technique, in which the joining partners initially come into contact with one another via a common contact surface, in which a solder material is already present or is introduced subsequently. The solder material located between the two joining partners is liquefied by heating and is distributed as uniformly as possible between the two joining partners. After the layer of solder which has formed between the two joining partners has cooled, a generally intimate material-to-material bond is formed.
However, if two components or joining partners which are exposed to extremely high thermal and mechanical loads are being joined, a particularly high-quality joining technique is needed. Without restricting the inventive idea which is to be described below, reference is made to a specific joining problem which is encountered in gas turbine engineering but which can quite easily be transferred to similar joining arrangements in other technical fields.
In particular, for cooling purposes it is appropriate to integrate what are known as impingement cooling plates within the platforms of gas turbine blades or vanes, in which cooling-channel systems are provided for effective cooling of the gas turbine blades or vanes. Impingement cooling plates are used for more efficient cooling of the inner blade or vane walls which surround the cooling system, so that the ability of the gas turbine blade or vane to withstand thermal loads can be improved decisively. The very extreme operating conditions to which a gas turbine blade or vane is exposed when a gas turbine is operating mean that all the components located inside a gas turbine blade or vane, as well as the joints between these components, must have an extremely high load-bearing capacity and mechanical and thermal reliability. Soldered joints which have to be able to withstand such adverse operating conditions and are to ensure a permanent join between the impingement cooling plate and the supporting regions within a platform in a gas turbine blade or vane are produced using liquid solder materials. Liquid solder materials are more suitable than alternative solder materials, for example in the form of solder foils, solder pastes or semiliquid fillers, especially since liquid solders, compared to other types of solder materials, are distributed as homogeneously as possible between two joining partners which are to be joined to one another.
The use of liquid solder materials provides for two joining partners to be brought into intimate contact via a common contact surface and for the liquid solder then to be introduced into the narrow gap between the two joining partners. The layer thickness of liquid solder which forms between the two joining partners from sides of a peripheral edge along their contact surface is typically between 0.03 and 0.05 mm. It is in fact the formation of a layer of liquid solder which is as homogeneous as possible between the two joining partners which makes an essential contribution to the quality of the soldered joint which is formed.
Since, according to the current prior art, the liquid solder is fed in along the peripheral edge of the contact surface between the two joining partners, which directly adjoin one another, there is no guarantee that the liquid solder material will be able to spread out over the entire depth of the contact surface. Particularly in the case of large-area contact surfaces between two joining partners which are to be joined to one another, surface regions which are at a relatively great distance from the peripheral edge of the contact surface may remain unwetted by the liquid solder material. Also, there are no direct ways of checking that the area between the two joining partners which are to be joined has been wetted with the liquid solder material. However, complete wetting of the contact surface with liquid solder is imperative if a permanent soldered joint is to be formed in particular for the abovementioned components used within a gas turbine blade or vane.
The object of the invention is to develop a device and a process for producing a soldered joint between two joining partners which can be joined via a common contact surface, using a solder material which can be introduced between the two joining partners, in such a manner that, using liquid solder material which is introduced between the two joining partners, it is possible to ensure that as far as possible the entire contact surface between the two joining partners is wetted with the liquid solder material. Moreover, it is to be possible to determine the extent to which the contact surface has been wetted with liquid solder material.
The solution to the object on which the invention is based is described in claim 1. Claim 8 relates to a process according to the invention. Features which advantageously refine the inventive idea form the subject matter of the subclaims and can be found in the further description, in particular with reference to the exemplary embodiments.
According to the invention, a device for producing a soldered joint between two joining partners which can be joined via a common contact surface, using a solder material which can be introduced between the two joining partners, is developed in such a manner that at least one joining partner, in the region of the contact surface, provides at least one recess, known as a solder reservoir, which faces the contact surface and into which the solder material can be introduced. Furthermore, the solder reservoir is completely delimited and surrounded by the contact surface.
The inventive idea provides, as an alternative to or in combination with the addition of liquid solder material through the peripheral gap between two joining partners which are fixedly joined to one another, the provision of liquid solder material in the middle of the contact surface between the two joining partners, as a result of at least one joining partner having a recess which is designed to be open toward the contact surface and in which liquid solder material has been or can be introduced. This joining partner is preferably a flat material in which the at least one recess, referred to below as a solder reservoir, passes all the way through the flat material. Consequently, it is possible for liquid solder material to be introduced into the solder reservoir when the two joining partners have already been assembled. However, solid joining partners can also be provided with recesses which are open on one side and into which recesses, which serve as solder reservoirs, liquid solder material is introduced before the two joining partners are assembled, and after the two joining partners have been assembled this liquid solder material can penetrate into the gap between the two joining partners.
The statements given below relate in general terms to the provision of solder reservoirs within joining partners which are designed as flat material, but it should be emphasized once again that the inventive idea can also be applied to the solid joining partners described above.
The recess, which is referred to as a solder reservoir, preferably has a slot-shaped contour which has edges which are as rounded as possible, in order to prevent fractures in the material. Moreover, in particular the peripheral edge of the solder reservoir which faces the contact surface is of rounded design, so that the liquid solder material which is present in the solder reservoir can penetrate into the gap between the two joining partners with as little difficulty as possible.
Depending on the size of the contact surface between the two joining partners which are to be joined, a multiplicity of solder reservoirs of this type can be provided, as far as possible arranged at equal distances from one another. The solder reservoirs are preferably arranged in such a manner as to ensure that the contact surface can be completely wetted by means of liquid solder material which can be supplied through the multiplicity of solder reservoirs provided. On the other hand, the reduction in the size of contact surface caused by the solder reservoirs should not be too great, so that the contact surface which is responsible for ensuring permanent joining retains the largest possible area.
Moreover, the provision of a multiplicity of solder reservoirs within a joining partner which is designed as flat material makes it possible to check whether the contact surface has been completely wetted with liquid solder material, by visual inspection through the solder reservoirs. In particular, the solder reservoirs can be used to establish whether solder material, starting from adjacent solder reservoirs, has propagated along the contact surface in the region of a respective solder reservoir even before the corresponding solder reservoir has been filled with liquid solder material.